The most effective way to troll these types of scams is to let them convince you, but repeatedly tell them that your computer froze and needs to be restarted. If they feel certain you're willing to pay, they will wait for the 20 minutes it takes to "restart" your computer. The more you "restart" your computer, time they invest in you, and the less costly that 20 minutes will seem.

That said I don't think I'd have the patience to do it more than once. And I suppose there are better ways to help humanity than trolling scammers.